This invention relates to latch constructions of the type provided for doors and the like, and more particularly to such latch constructions having bolt operating improvements. Even more particularly, this invention relates to one or both of two distinct areas of bolt operating improvement, one of transferring motion from a latch bolt to an operator therefor in order to smoothly and efficiently operate the latch, and the other of transferring motion between an auxiliary bolt and a main bolt when the auxiliary bolt is provided to ensure positive dogging of the main bolt in an improved manner with maximum resistance against attempted violation thereof. Furthermore, this invention may further include an improved backset adjustment added to either or both of the foregoing to provide maximum adjustment versatility where that is desired in the overall combination. Most prior latch constructions of the type provided for doors and the like in their transferring of motion from their rearward operator forwardly through their latch operating mechanism into the bolt thereof have necessarily been of quite a complex nature if the latch construction is to continuously operate in the required dependable manner, while still being resistant to violation by outside forces. This is particularly true of the spring latch type which requires positive mechanical motion for movement from bolt engaged to bolt disengaged positions, but makes use of merely spring pressure for opposite movement back to the bolt engaged position. There is a clear want and need for a more simplified mechanical structure serving the required mechanical motion and yet one which will provide equivalent or increased positive dependability regardless of the direction of motion transfer, that is, the mechanical motion during bolt disengagement or the spring derived motion of the bolt re-engagement.
Furthermore, in keeping with the modern trends in our society, latch constructions regardless of the type thereof although particularly applicable to spring latch constructions, particularly require any possible increases in security while still maintaining the latch construction reasonably conveniently usable. One of the major increases is that of bolt projection, for instance, from the door into the keeper of the door frame. Few will argue that increased bolt projection provides increased security yet these increases must be contained within a limited amount of space in order to make the particular latch construction of a viable nature. It, therefore, becomes a goal in latch constructions to provide the motion transfer elements not only of proper use, but clearly with maximum adjustment versatility within the overall construction so that the maximum of mechanical advantages may be incorporated therein.
Still in keeping with the foregoing violation deterrents, another obvious area which can always be improved in latch constructions of the spring latch type is the dogging of the main bolt by the auxiliary bolt for engagement securement. In most prior spring latch constructions, the dogging or blocking for movement has usually been carried out by a locking dog between the main bolt and the auxiliary bolt so that with the main bolt extended engaging the strike within the door frame and the auxiliary bolt retracted by the strike, the locking dog bears against the main bolt retaining it in its extended position. Furthermore, this particular positioning arrangement requires lost motion connections between various construction elements which can only operate if very precisely manufactured and assembled. Thus, the area for improvement is the reduction of the lost motion connections to a minimal amount and the formation of those that remain in a relatively simplified manner so as to be positively operable.